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<h2><a name="SECTION00202100000000000000000">
18.2.10 Common problems and solutions</a>
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<p>

<ul>
<li>Most HTTP servers buffer the output from CGI scripts until the
script is completed.  This means that it is not possible to display a
progress report on the client's display while the script is running.

<p>
</li>
<li>Check the installation instructions above.

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</li>
<li>Check the HTTP server's log files.  ("<tt class="samp">tail -f logfile</tt>" in a
separate window may be useful!)

<p>
</li>
<li>Always check a script for syntax errors first, by doing something
like "<tt class="samp">python script.py</tt>".

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</li>
<li>If your script does not have any syntax errors, try adding
"<tt class="samp">import cgitb; cgitb.enable()</tt>" to the top of the script.

<p>
</li>
<li>When invoking external programs, make sure they can be found.
Usually, this means using absolute path names -- <a class="envvar" id='l2h-3831' xml:id='l2h-3831'>PATH</a> is
usually not set to a very useful value in a CGI script.

<p>
</li>
<li>When reading or writing external files, make sure they can be read
or written by the userid under which your CGI script will be running:
this is typically the userid under which the web server is running, or some
explicitly specified userid for a web server's "<tt class="samp">suexec</tt>" feature.

<p>
</li>
<li>Don't try to give a CGI script a set-uid mode.  This doesn't work on
most systems, and is a security liability as well.
</li>
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<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
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